Composite catalyst, preparation method and application thereof, and method for synthesizing dimethyl ether from synthesis gas through one-step method

Abstract

The invention relates to a composite catalyst, a preparation method and application thereof and a method for synthesizing dimethyl ether from synthesis gas through a one-step method.The composite catalyst comprises a component A and a component B. The component A is a coralline-shaped copper-zinc-aluminum catalyst, and the coralline-shaped copper-zinc-aluminum catalyst comprises copper, zinc and aluminum; the microstructure is in a coralline shape formed by sheet nanorods; and the component B is an HZSM-5 molecular sieve. When the composite catalyst is applied to synthesis of dimethyl ether from synthesis gas, the temperature in the synthesis gas conversion process can be effectively reduced, generation of by-products is reduced, and the raw material conversion rate and the dimethyl ether selectivity are improved.

Description

Technical Field

[0001] This invention relates to a composite catalyst, its preparation method and application, and a method for one-step synthesis of dimethyl ether from syngas. Background Technology

[0002] Since the 1980s, dimethyl ether (DME) has become an important chemical intermediate that countries have been vying to develop. It plays a vital role in the pharmaceutical, fuel, and pesticide industries, not only replacing Freon as a refrigerant to reduce ozone layer depletion but also serving as a substitute for city gas and liquefied petroleum gas (LPG). Currently, there are two main processes for synthesizing DME: one is a two-step process where syngas is first synthesized into methanol, then dehydrated to produce DME; the other is a one-step process using a composite catalyst to synthesize DME from syngas. The one-step process, employing a composite catalyst system, allows syngas to immediately undergo dehydration on the dehydration component after methanol is produced on the methanol synthesis catalyst, thus overcoming the thermodynamic equilibrium limitations of methanol synthesis and significantly increasing the conversion rate of carbon monoxide.

[0003] CN1356163A discloses a bifunctional catalyst composed of copper and zinc composite oxides as methanol synthesis components and alumina as the active component for methanol dehydration. The catalyst was developed under the following conditions: H2 / CO molar ratio of 3.85, reaction temperature of 300℃, reaction pressure of 4 MPa, and feed gas space velocity of 1490 h⁻¹. -1 Under the given reaction conditions, the conversion rate of carbon monoxide was 81.75%, and the selectivity for dimethyl ether was 93.56%. The above catalyst had a high reaction temperature and a low conversion rate of carbon monoxide.

[0004] Because the optimal activity temperature of activated Al2O3 as a methanol dehydration catalyst is relatively high (approximately 300°C), it does not match the optimal activity temperature of copper-based catalysts used in methanol synthesis (approximately 250°C), leading to a decrease in the performance of bifunctional catalysts. Research has been conducted using various molecular sieve catalysts as active components for methanol dehydration.

[0005] US6638892 discloses a bifunctional catalyst using H-type Y zeolite as the active component for methanol dehydration. This catalyst is suitable for use in syngas reactions with a composition of H2 / CO / CO2 = 74.8 / 20.1 / 5.1, a reaction temperature of 270°C, a reaction pressure of 500 psig, and a feed gas space velocity of 1140 h⁻¹. -1 Under the given reaction conditions, the conversion rate of carbon monoxide was 79.2%, and the selectivity of dimethyl ether in the organic products was 87.7%. However, under the same conditions, when alumina was used as the methanol dehydration component, the carbon monoxide conversion rate and dimethyl ether selectivity were 68.5% and 55.4%, respectively. This demonstrates that replacing Al₂O₃ with Y molecular sieve can simultaneously improve both the CO conversion rate and the dimethyl ether selectivity. Summary of the Invention

[0006] This invention addresses the problems of high reaction temperature, low carbon monoxide conversion rate, and / or low dimethyl ether selectivity in the one-step synthesis of dimethyl ether from syngas in existing technologies, and provides a novel composite catalyst. The composite catalyst of this invention, used in the syngas-to-dimethyl ether reaction, features low reaction temperature, high carbon monoxide conversion rate, and high dimethyl ether selectivity.

[0007] This invention provides a composite catalyst comprising component A and component B. Component A is a coral-like copper-zinc-aluminum catalyst, the constituent elements of which include copper, zinc, and aluminum, and the microstructure is coral-like, composed of thin sheet nanorods. Component B is an HZSM-5 molecular sieve.

[0008] In the composite catalyst of the present invention, the weight ratio of component A to component B can be selected from a wide range and can be specifically determined as needed. According to a preferred embodiment of the present invention, the weight ratio of component A to component B is 4-1:1.

[0009] In the composite catalyst of the present invention, there are no special requirements for the HZSM-5 molecular sieve. Commonly used HZSM-5 molecular sieves can be used in the present invention. According to a preferred embodiment of the present invention, the present invention preferably uses HZSM-5 molecular sieve with a high silicon-to-aluminum ratio. Preferably, the SiO2:Al2O3 molar ratio of the HZSM-5 molecular sieve is 150-400:1.

[0010] In this invention, the coral-like copper-zinc-aluminum catalyst with the aforementioned composition and microstructure is used in composite catalysts, and is particularly suitable for one-step synthesis of dimethyl ether. It can effectively improve the conversion rate of raw materials and the selectivity of dimethyl ether at lower operating temperatures.

[0011] In this invention, the specific surface area of ​​the coral-like copper-zinc-aluminum catalyst is not particularly limited. Any suitable specific surface area can be selected as long as it achieves the objective of this invention. According to a preferred embodiment of this invention, the specific surface area of ​​the coral-like copper-zinc-aluminum catalyst is 85-110 m². 2 / g.

[0012] In this invention, there are no special requirements for the composition of the coral-like copper-zinc-aluminum catalyst, and the amount of each element can be selected from a wide range. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the molar ratio of aluminum to zinc is 0.3-1.

[0013] According to a preferred embodiment of the present invention, the content of copper as oxide is 50-70 wt%, preferably 54-64 wt%, based on the total weight of the coral-like copper-zinc-aluminum catalyst, and the total content of aluminum as oxide and zinc as oxide is 30-50 wt%, preferably 35-46 wt%.

[0014] In this invention, the form in which copper, zinc, and aluminum exist in the coral-like copper-zinc-aluminum catalyst is not particularly required, and is similar to existing technologies.

[0015] Generally, when storing coral-like copper-zinc-aluminum catalysts, one or more of copper, zinc, and aluminum exist in oxide form, preferably all of them exist in oxide form.

[0016] Generally, when using coral-like copper-zinc-aluminum catalysts, copper exists in a reduced form, while the rest exist in oxide form.

[0017] According to the present invention, the coral-like copper-zinc-aluminum catalyst may further include a metal element M, wherein the metal element M is selected from one or more of zirconium, tin, lead, lanthanum, and cerium, preferably lanthanum and / or cerium.

[0018] In this invention, the amount of the auxiliary element can be selected from a wide range. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the content of the metal element M, calculated as oxide, is 0.01-20 wt% based on the total weight of the catalyst, preferably 1-5 wt%.

[0019] In this invention, the form in which the metallic element M exists in the coral-like copper-zinc-aluminum catalyst is not particularly required.

[0020] Generally, when coral-like copper-zinc-aluminum catalysts are stored, the metal element M exists in the form of an oxide.

[0021] Generally, when using coral-like copper-zinc-aluminum catalysts, the metal element M exists in the form of an oxide.

[0022] Coral-shaped copper-zinc-aluminum catalysts with the aforementioned characteristics all possess the advantages described in this invention, and their preparation methods have no special requirements. This invention unexpectedly discovered a particularly simple method for preparing the coral-shaped copper-zinc-aluminum catalyst of this invention. Accordingly, this invention provides a method for preparing a copper-zinc-aluminum catalyst, which includes: co-precipitating a copper source, an aluminum source, and a zinc source in solution under pressure conditions, and drying and calcining the resulting solid; the pressure conditions are higher than atmospheric pressure.

[0023] In the preparation method of the copper-zinc-aluminum catalyst of the present invention, the pressure can be selected within a wide range. The following is an illustrative description, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the pressure is 1-3 MPa, for example, 1.2 MPa, 1.5 MPa, 1.8 MPa, 2.2 MPa, 2.5 MPa, or 2.8 MPa.

[0024] In the preparation method of the copper-zinc-aluminum catalyst in this invention, there are no special requirements for the pressure environment. The pressure environment can be provided by introducing various gases, such as air, oxygen, inert gases, etc. In the embodiments of this invention, nitrogen is used to illustrate the specific implementation of this invention, but this does not limit the scope of this invention.

[0025] In the preparation method of the copper-zinc-aluminum catalyst of the present invention, the temperature of co-precipitation is not particularly limited. As long as the purpose of the present invention can be achieved, any suitable temperature can be selected. According to a preferred embodiment of the present invention, the temperature of co-precipitation is 50-80℃.

[0026] In the preparation method of the copper-zinc-aluminum catalyst of the present invention, the co-precipitation time is not particularly limited. As long as the purpose of the present invention can be achieved, any suitable time can be selected. According to a preferred embodiment of the present invention, the co-precipitation time is 0.5-2h.

[0027] In the preparation method of the copper-zinc-aluminum catalyst of the present invention, it is well known that co-precipitation is carried out under alkaline conditions. However, the difference is that the pH of the material after co-precipitation is preferably 6-8.

[0028] In the preparation method of the copper-zinc-aluminum catalyst of the present invention, there are no special requirements for the specific form of the coprecipitation, which can be static or dynamic. According to a preferred embodiment of the present invention, the coprecipitation is carried out in a dynamic environment.

[0029] In the preparation method of the copper-zinc-aluminum catalyst in this invention, there are no special requirements for the drying and calcination conditions. Commonly used conditions are applicable to this invention. The following is an illustrative description, but it does not limit the scope of this invention.

[0030] According to a preferred embodiment of the present invention, in the preparation method of the copper-zinc-aluminum catalyst, the drying temperature is 60-80°C.

[0031] According to a preferred embodiment of the present invention, in the preparation method of the copper-zinc-aluminum catalyst, the drying time is 12-36 h.

[0032] According to a preferred embodiment of the present invention, in the preparation method of the copper-zinc-aluminum catalyst, calcination is carried out at a low temperature, preferably 290-330°C.

[0033] In the preparation method of the copper-zinc-aluminum catalyst of the present invention, there is no special requirement for the calcination time, which can be selected and determined according to the temperature. According to a preferred embodiment of the present invention, the calcination time is 2-6 hours.

[0034] In the preparation method of the copper-zinc-aluminum catalyst of the present invention, there are no special requirements for the amount of each raw material. The specific selection and feeding are based on the needs of the catalyst composition. According to a preferred embodiment of the present invention, the amount of copper source, aluminum source and zinc source is such that the molar ratio of aluminum to zinc is 0.3-1.

[0035] According to a preferred embodiment of the present invention, in the preparation process of the copper-zinc-aluminum catalyst, the amounts of copper source, aluminum source and zinc source are such that, based on the total weight of the copper-zinc-aluminum catalyst, the content of copper as oxide is 50-70 wt%, preferably 54-64 wt%, and the total content of aluminum as oxide and zinc as oxide is 30-50 wt%, preferably 35-46 wt%.

[0036] In the preparation process of the copper-zinc-aluminum catalyst of the present invention, other elements can be added arbitrarily according to the needs of use to synthesize the copper-zinc-aluminum catalyst. According to a preferred embodiment of the present invention, the contact is carried out in the presence of a metal M source, wherein the metal M element is selected from one or more of zirconium, tin, lead, lanthanum, and cerium, preferably lanthanum and / or cerium.

[0037] In the preparation process of the copper-zinc-aluminum catalyst of the present invention, the amount of metal M source can be selected from various ranges according to the needs of use. The following is an illustrative description, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the amount of metal M source is such that, based on the total weight of the copper-zinc-aluminum catalyst, the content of the metal M element as oxide is 0.01-20 wt%, preferably 1-5 wt%.

[0038] In the preparation method of the copper-zinc-aluminum catalyst of the present invention, the copper source is not particularly limited. Any suitable copper source can be selected as long as it can achieve the purpose of the present invention. According to a preferred embodiment of the present invention, the copper source is selected from one or more soluble copper salts, such as copper sulfate, copper chloride, copper nitrate, copper acetate, and copper oxalate.

[0039] In the preparation method of the copper-zinc-aluminum catalyst of the present invention, the aluminum source is not particularly limited. Any suitable aluminum source can be selected as long as it can achieve the purpose of the present invention. According to a preferred embodiment of the present invention, the aluminum source is selected from one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum acetate, and aluminum oxalate.

[0040] In the preparation method of the copper-zinc-aluminum catalyst of the present invention, the type of zinc source can be selected from a wide range. The following is an illustrative description, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the zinc source is selected from one or more of zinc sulfate, zinc chloride, zinc nitrate, zinc acetate, and zinc oxalate.

[0041] In the preparation method of the copper-zinc-aluminum catalyst of the present invention, the coprecipitant is not particularly limited. Any suitable coprecipitant can be selected as long as it can achieve the purpose of the present invention. According to a preferred embodiment of the present invention, the coprecipitant is selected from one or more of alkali metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates, preferably alkali metal carbonates, and more preferably sodium carbonate.

[0042] In the preparation method of the copper-zinc-aluminum catalyst of this invention, in order to obtain a solid intermediate product for calcination, the materials after contact can be subjected to solid-liquid separation. The separation method can be freely selected, for example, it can be obtained by filtration; in addition, the solid obtained by filtration can be subjected to other conventional treatments, such as washing, but this does not limit the scope of the invention.

[0043] The preparation method of the composite catalyst of the present invention has no special requirements. It can be obtained simply by mixing and pulverizing, or by molding as needed.

[0044] In an embodiment of the present invention, component A and component B of the present invention are mixed in a weight ratio to obtain a powdered composite catalyst.

[0045] The composite catalyst of the present invention is particularly suitable for gas-liquid-solid three-phase bed reactors, i.e. slurry bed reactors.

[0046] In this invention, the composite catalyst has a wide range of applications. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, this invention provides an application of the composite catalyst described herein in the one-step preparation of dimethyl ether from syngas.

[0047] Specifically, the present invention provides a method for one-step synthesis of dimethyl ether from syngas, the method comprising: catalytically converting syngas into dimethyl ether in the presence of the composite catalyst described in the present invention.

[0048] In this invention, there are no special requirements for the specific composition of the syngas. Commonly used compositions can be used in this invention. For example, syngas generally contains CO, CO2 and H2, and its specific composition is not particularly required. For example, the composition (v / v) is: CO:H2 = 1:1-10. The carbon dioxide content can be selected within a wide range, for example, 1-10v.

[0049] In this invention, there are no special requirements for the conditions of catalytic conversion to synthesize dimethyl ether. It is worth noting that this invention can be carried out at low temperatures, with a catalytic conversion temperature range of 240-280℃, for example, 240℃, 245℃, 250℃, 255℃, 260℃, 265℃, 270℃, 275℃, 280℃, etc. In contrast, the temperature range of existing technologies generally requires temperatures higher than 270℃, for example, above 270℃. The advantages of the composite catalyst of this invention at low temperatures are illustrated by comparing Example 1 and Comparative Example 1. Other composite catalysts of this invention can also react at low temperatures and possess the aforementioned advantages.

[0050] Other catalytic conversion conditions have no special requirements, such as a pressure of 3-6 MPa and a syngas space velocity of 500-2000 mL / g. 催化剂 h -1 .

[0051] The composite catalyst of the present invention is particularly suitable for use under gas-liquid-solid three-phase reaction conditions. Therefore, the present invention preferably carries out the catalytic conversion synthesis of dimethyl ether in the presence of a solvent. There are no special requirements for the solvent, such as liquid paraffin. The amount of solvent can be selected in a wide range, such as 50-200 mL / g catalyst.

[0052] The composite catalyst provided by this invention is particularly suitable for the slurry bed synthesis of dimethyl ether from syngas. The reaction conditions are generally as follows: the liquid solvent is liquid paraffin, the reaction temperature is 240-280℃, and the reaction pressure is 3-6MPa.

[0053] As is known, the composite catalyst prepared by this invention generally needs to be reduced before the reaction. There are no special requirements for the composition of the reducing gas or the reduction conditions. For example, the reducing gas can be a mixture of hydrogen and nitrogen, wherein the hydrogen content is 1-10%, and the reduction temperature can be 200-250℃.

[0054] The composite catalyst of this invention can effectively reduce the temperature during the synthesis of dimethyl ether, reduce the generation of by-products, and improve the conversion rate of raw materials and the selectivity of dimethyl ether.

[0055] Using the composite catalyst of the present invention, dimethyl ether can be synthesized by high conversion and high selectivity at lower temperatures. Attached Figure Description

[0056] Figure 1 The image shows the scanning electron microscope (SEM) characterization of the CuO / ZnO / Al2O3 catalyst CZA-1 prepared in Example 1.

[0057] Figure 2 Scanning electron microscopy (SEM) characterization of the CuO / ZnO / Al2O3 catalyst CZA-a prepared for Comparative Example 1. Detailed Implementation

[0058] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0059] The specific embodiments of the present invention will be described in detail below. However, it should be noted that the scope of protection of the present invention is not limited to these specific embodiments, but is determined by the claims in the appendix.

[0060] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0061] When this specification uses the prefixes "known to those skilled in the art," "prior art," or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those conventionally used in the art at the time the invention was proposed, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0062] It should be noted that the two or more aspects (or embodiments) disclosed in the context of this specification can be arbitrarily combined with each other, and the resulting technical solutions (such as methods or systems) are part of the original disclosure of this specification and also fall within the protection scope of this invention.

[0063] The present invention will be described in detail below through embodiments. In the following embodiments,

[0064] 1. Raw materials

[0065] The reagents for elements such as copper, aluminum, zinc, zirconium, tin, lead, lanthanum, and cerium, as well as alkali metal hydroxides and carbonates used in this invention, were all purchased from Sinopharm Reagent and were all of analytical grade.

[0066] 2. Testing Method

[0067] Specific surface area was measured using a Micrometrics Tristar 3000 specific surface area analyzer.

[0068] Surface morphology was tested using a scanning electron microscope (ZEISS Merlin) and a transmission electron microscope (Tecnai 20S-TWIN).

[0069] Activity test condition 1:

[0070] 3g of the composite catalyst and 300mL of liquid paraffin were loaded into a 500mL reactor. After reduction with a 5% H2 / N2 mixture at 250℃, the mixture was switched to syngas with a composition of (H2 / CO = 2, CO2 4%). The reaction temperature was 250℃, the reaction pressure was 5MPa, and the syngas space velocity was 1000mL / g. 催化剂 h -1 .

[0071] Dimethyl ether selectivity refers to the proportion of dimethyl ether in the total organic products.

[0072] Example 1

[0073] Preparation of copper-zinc-aluminum catalyst: 50g of copper nitrate trihydrate, 30.8g of zinc nitrate hexahydrate, and 11.6g of aluminum nitrate nonahydrate were added to 100mL of water and stirred until dissolved. The solution was then transferred to a 500mL high-pressure reactor, sealed, and heated to 60℃. Nitrogen gas was then introduced into the reactor to 2MPa. A basic alkaline solution was prepared by adding 40g of sodium carbonate to 100mL of water. This alkaline solution was slowly added to the reactor using a liquid phase pump while stirring. After the alkaline solution was added, heating and stirring continued for 2 hours. After completion, the reactor was allowed to cool naturally, the pressure was released, and the pH of the solution was measured to be 7.5. The precipitate was filtered and washed with water until the filtrate was neutral. The precipitate was dried in a 60℃ oven for 24 hours and then calcined at 300℃ for 4 hours to obtain the CuO / ZnO / Al2O3 catalyst, designated CZA-1.

[0074] Figure 1 The image shows a scanning electron microscope (SEM) characterization of the CuO / ZnO / Al2O3 catalyst CZA-1 prepared in Example 1. The morphology is coral-like, composed of thin sheet nanorods with a width of 30-40 nm.

[0075] Specific surface area is 96m² 2 / g;

[0076] Preparation of composite catalyst: CZA-1 catalyst and HZSM-5 molecular sieve with a silicon-to-aluminum ratio of 300 were mixed in a mass ratio of 3:2 and passed through a 100-mesh sieve to obtain composite catalyst numbered CZA-1 / 300.

[0077] According to activity test condition 1: CO conversion rate was 83.5%, and dimethyl ether selectivity was 96.1%.

[0078] Example 2

[0079] Preparation of copper-zinc-aluminum catalyst: 50g of copper nitrate trihydrate, 24.7g of zinc nitrate hexahydrate, and 18.4g of aluminum nitrate nonahydrate were added to 100mL of water and stirred until dissolved. The solution was then transferred to a 500mL high-pressure reactor, sealed, and heated to 80℃. Nitrogen gas was then introduced into the reactor to 2MPa. 46g of sodium carbonate was dissolved in 100mL of water to prepare an alkaline solution. This alkaline solution was slowly added to the reactor using a liquid phase pump while stirring. After the alkaline solution was added, heating and stirring continued for 0.5h. After completion, the reactor was allowed to cool naturally, the pressure was released, and the pH of the solution was measured to be 8. The precipitate was filtered and washed with water until the filtrate was neutral. The precipitate was dried in an 80℃ oven for 24h and then calcined at 300℃ for 3h to obtain the CuO / ZnO / Al2O3 catalyst, designated CZA-2.

[0080] The morphology is characterized as coral-like, composed of thin nanorod sheets, with a width of 30-40 nm.

[0081] Specific surface area is 100m² 2 / g;

[0082] The preparation of the composite catalyst is the same as in Example 1;

[0083] According to activity test condition 1: CO conversion rate was 81%, and dimethyl ether selectivity was 96.3%.

[0084] Example 3

[0085] Preparation of copper-zinc-aluminum catalyst: 50g of copper nitrate trihydrate, 31.5g of zinc nitrate hexahydrate, and 39.7g of aluminum nitrate nonahydrate were added to 100mL of water and stirred until dissolved. The solution was then transferred to a 500mL high-pressure reactor, sealed, and heated to 50℃. Nitrogen gas was then introduced into the reactor to 2MPa. 46g of sodium carbonate was dissolved in 100mL of water to prepare an alkaline solution. This alkaline solution was slowly added to the reactor using a liquid phase pump while stirring. After the alkaline solution was added, heating and stirring continued for 1 hour. After completion, the reactor was allowed to cool naturally, the pressure was released, and the pH of the solution was measured to be 6. The precipitate was filtered and washed with water until the filtrate was neutral. The precipitate was dried in an 80℃ oven for 24 hours and then calcined at 290℃ for 2 hours to obtain the CuO / ZnO / Al2O3 catalyst, designated CZA-3.

[0086] The morphology is characterized as coral-like, composed of thin nanorod sheets, with a width of 30-40 nm.

[0087] Specific surface area is 110 m² 2 / g;

[0088] The preparation of the composite catalyst is the same as in Example 1;

[0089] According to activity test condition 1: CO conversion rate was 82%, and dimethyl ether selectivity was 96.5%.

[0090] Example 4

[0091] Preparation of copper-zinc-aluminum catalyst: 50g of copper nitrate trihydrate, 27.7g of zinc nitrate hexahydrate, and 25.9g of aluminum nitrate nonahydrate were added to 100mL of water and stirred until dissolved. The solution was then transferred to a 500mL high-pressure reactor, sealed, and heated to 70℃. Nitrogen gas was then introduced into the reactor to 3MPa. 42g of sodium carbonate was dissolved in 100mL of water to prepare an alkaline solution. This alkaline solution was slowly added to the reactor using a liquid phase pump while stirring. After the alkaline solution was added, heating and stirring continued for 2 hours. After the reaction, the reactor was allowed to cool naturally, the pressure was released, and the pH of the solution was measured to be 7. The precipitate was filtered and washed with water until the filtrate was neutral. The precipitate was dried in an oven at 80℃ for 24 hours and then calcined at 330℃ for 2 hours to obtain the CuO / ZnO / Al2O3 catalyst, designated CZA-4.

[0092] The morphology is characterized as coral-like, composed of thin nanorod sheets, with a width of 30-40 nm.

[0093] Specific surface area is 85m² 2 / g;

[0094] The preparation of the composite catalyst is the same as in Example 1;

[0095] According to activity test condition 1: CO conversion rate was 82%, and dimethyl ether selectivity was 95.9%.

[0096] Example 5

[0097] Preparation of copper-zinc-aluminum catalyst: 50g of copper nitrate trihydrate, 24.6g of zinc nitrate hexahydrate, 19.4g of aluminum nitrate nonahydrate, and 1.4g of lanthanum nitrate hexahydrate were added to 100mL of water and stirred until dissolved. The solution was then transferred to a 500mL high-pressure reactor, sealed, and heated to 70℃. Nitrogen gas was then introduced into the reactor to 2MPa. 42g of sodium carbonate was dissolved in 100mL of water to prepare an alkaline solution. This alkaline solution was slowly added to the reactor using a liquid phase pump while stirring. After the alkaline solution was added, heating and stirring continued for 2 hours. After the reaction, the reactor was allowed to cool naturally, the pressure was released, and the pH of the solution was measured to be 7.5. The precipitate was filtered and washed with water until the filtrate was neutral. The precipitate was dried in a 70℃ oven for 24 hours and then calcined at 300℃ for 3 hours to obtain the CuO / ZnO / Al2O3 / La2O3 catalyst, designated CZA-5.

[0098] The morphology is characterized as coral-like, composed of thin nanorod sheets, with a width of 30-40 nm.

[0099] Specific surface area is 99m²2 / g;

[0100] The preparation of the composite catalyst is the same as in Example 1;

[0101] According to activity test condition 1: CO conversion rate was 86%, and dimethyl ether selectivity was 95.8%.

[0102] Example 6

[0103] Preparation of copper-zinc-aluminum catalyst: 50g copper nitrate trihydrate, 24.6g zinc nitrate hexahydrate, 19.4g aluminum nitrate nonahydrate, and 2.02g cerium nitrate hexahydrate were added to 100mL of water and stirred until dissolved. The solution was then transferred to a 500mL high-pressure reactor, sealed, and heated to 70℃. Nitrogen gas was then introduced into the reactor to 1MPa. 42g sodium carbonate was dissolved in 100mL of water to prepare an alkaline solution. This alkaline solution was slowly added to the reactor using a liquid phase pump while stirring. After the alkaline solution was added, heating and stirring continued for 2 hours. After the reaction, the reactor was allowed to cool naturally, the pressure was released, and the pH of the solution was measured to be 7.5. The precipitate was filtered and washed with water until the filtrate was neutral. The precipitate was dried in a 70℃ oven for 24 hours and then calcined at 300℃ for 4 hours to obtain the CuO / ZnO / Al2O3 / CeO2 catalyst, designated CZA-6.

[0104] The morphology is characterized as coral-like, composed of thin nanorod sheets, with a width of 30-40 nm.

[0105] Specific surface area is 103 m² 2 / g;

[0106] The preparation of the composite catalyst is the same as in Example 1;

[0107] According to activity test condition 1: CO conversion rate was 86%, and dimethyl ether selectivity was 96.4%.

[0108] Example 7

[0109] Preparation of copper-zinc-aluminum catalyst: Following the method of Example 1, except that the pressure was 4 MPa, a CuO / ZnO / Al2O3 catalyst was obtained, designated CZA-7.

[0110] The morphology is characterized as coral-like structures composed of thin nanorod sheets, with a width of 40-80 nm.

[0111] Specific surface area is 83m² 2 / g;

[0112] The preparation of the composite catalyst is the same as in Example 1;

[0113] According to activity test condition 1: CO conversion rate was 74%, and dimethyl ether selectivity was 95%.

[0114] Example 8

[0115] Preparation of copper-zinc-aluminum catalyst: Following the method of Example 1, except that the pressure was 0.5 MPa, a CuO / ZnO / Al2O3 catalyst was obtained, designated CZA-8.

[0116] The morphology is characterized as coral-like, composed of thin nanorod sheets, with a width of 60-90 nm.

[0117] Specific surface area is 86m² 2 / g;

[0118] The preparation of the composite catalyst is the same as in Example 1;

[0119] According to activity test condition 1: CO conversion rate was 72%, and dimethyl ether selectivity was 94.3%.

[0120] Example 9

[0121] The method is the same as in Example 1, except that the composite catalyst is prepared by mixing CZA-1 catalyst with HZSM-5 molecular sieve with a silicon-to-aluminum ratio of 150 at a mass ratio of 4:1.

[0122] According to activity test condition 1: CO conversion rate was 82%, and dimethyl ether selectivity was 95.8%.

[0123] Example 10

[0124] The method is the same as in Example 1, except that the composite catalyst is prepared by mixing CZA-1 catalyst with HZSM-5 molecular sieve with a silicon-to-aluminum ratio of 400 at a mass ratio of 1:1.

[0125] According to activity test condition 1: CO conversion rate was 83%, and dimethyl ether selectivity was 95.0%.

[0126] Example 11

[0127] The method is the same as in Example 1, except that the composite catalyst is prepared by mixing CZA-1 catalyst with HZSM-5 molecular sieve with a silicon-to-aluminum ratio of 300 at a mass ratio of 6:1.

[0128] According to activity test condition 1: CO conversion rate was 70%, and dimethyl ether selectivity was 85.0%.

[0129] Example 12

[0130] The method is the same as in Example 1, except that the composite catalyst is prepared using HZSM-5 molecular sieve with a silicon-to-aluminum ratio of 500.

[0131] According to activity test condition 1: CO conversion rate was 68%, and dimethyl ether selectivity was 80%.

[0132] Comparative Example 1

[0133] Preparation of copper-zinc-aluminum catalyst: 50g of copper nitrate trihydrate, 30.8g of zinc nitrate hexahydrate, and 11.6g of aluminum nitrate nonahydrate were added to 100mL of water and stirred until dissolved. The solution was then transferred to a 500mL beaker and heated to 60℃. 40g of sodium carbonate was then dissolved in 100mL of water to prepare an alkaline solution. This alkaline solution was slowly added to the beaker using a liquid-phase pump while stirring. After the alkaline solution was added, heating and stirring continued for 2 hours. After the addition was complete, the solution was allowed to cool naturally, and the pH was measured to be 7.5. The precipitate was filtered and washed with water until the filtrate was neutral. The precipitate was then dried in a 60℃ oven for 24 hours and calcined at 300℃ for 4 hours to obtain the CuO / ZnO / Al2O3 catalyst, designated CZA-a.

[0134] Morphological characterization: Coral-like structure composed of thin-film nanorods, such as... Figure 2 ;

[0135] Specific surface area is 80m² 2 / g;

[0136] The preparation of the composite catalyst is the same as in Example 1;

[0137] According to activity test condition 1: CO conversion rate was 40%, and dimethyl ether selectivity was 92%.

[0138] Activity test conditions 2: 3g of the composite catalyst and 300mL of liquid paraffin were placed in a 500mL reactor. After reduction with a 5% H2 / N2 mixture at 250℃, the mixture was switched to syngas with a composition of (H2 / CO = 2.3, CO2 4%). The reaction temperature was 240℃, the reaction pressure was 5MPa, and the syngas space velocity was 1000mL / g. 催化剂 h -1 The activity evaluation results of the composite catalysts prepared in Example 1 and Comparative Example 1 are shown in Table 1 below.

[0139] Table 1

[0140] Catalyst source CO conversion rate / % Dimethyl ether selectivity / % Example 1 75 98 Comparative Example 1 22 94

[0141] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A composite catalyst, characterized in that, The composite catalyst comprises component A and component B. Component A is a coral-like copper-zinc-aluminum catalyst, which is composed of copper, zinc and aluminum, and has a microstructure of coral-like structure composed of thin sheet nanorods. Component B is HZSM-5 molecular sieve.

2. The composite catalyst according to claim 1, wherein, The weight ratio of component A to component B is 4-1:1; and / or The SiO2:Al2O3 molar ratio of the HZSM-5 molecular sieve is 150-400:

1.

3. The composite catalyst according to claim 1 or 2, wherein, The properties of component A, a coral-like copper-zinc-aluminum catalyst, include: The width of the thin-film nanorods is 30-40 nm; and / or Specific surface area is 85-110 m² 2 / g; and / or The molar ratio of aluminum to zinc is 0.3-1.

4. The composite catalyst according to any one of claims 1-3, wherein, The properties of component A, a coral-like copper-zinc-aluminum catalyst, include: The total weight of the catalyst, based on copper oxide, is 50-70 wt%, preferably 54-64 wt%, and the total content of aluminum oxide and zinc oxide is 30-50 wt%, preferably 35-46 wt%; and / or When storing the catalyst, one or more of copper, zinc, and aluminum are present in oxide form, preferably all of copper, zinc, and aluminum are present in oxide form; and / or When the catalyst is used, copper exists in a reduced form, while the rest exist in oxide form.

5. The composite catalyst according to any one of claims 1-4, wherein, The properties of component A, a coral-like copper-zinc-aluminum catalyst, include: The constituent elements also include a metallic element M, which is selected from one or more of zirconium, tin, lead, lanthanum, and cerium, preferably lanthanum and / or cerium; Preferably, the content of the metal M element, calculated as oxide, is 0.01-20 wt% based on the total weight of the catalyst, and more preferably 1-5 wt%. Preferably, when the catalyst is stored, the metal element M exists in the form of an oxide; and / or When the catalyst is used, the metal element M exists in the form of an oxide.

6. The composite catalyst according to any one of claims 1-5, wherein, The preparation method of component A, a coral-like copper-zinc-aluminum catalyst, includes: co-precipitating copper, aluminum, and zinc sources in solution under pressure conditions, and drying and calcining the resulting solid; the pressure conditions are higher than atmospheric pressure.

7. The composite catalyst according to claim 6, wherein, In the preparation method of component A, the coral-like copper-zinc-aluminum catalyst: The pressure is 1-3 MPa; and / or The conditions for coprecipitation include: The temperature is 50-80℃; and / or the time is 0.5-2h; and / or the pH of the material after co-precipitation is 6-8; and / or it is carried out in a dynamic environment; and / or The drying conditions include: a temperature of 60-80℃; and / or a time of 12-36 hours; and / or The roasting conditions include a temperature of 290-330℃ and / or a time of 2-6 hours.

8. The composite catalyst according to any one of claims 6-7, wherein, The copper source is selected from one or more of copper sulfate, copper chloride, copper nitrate, copper acetate, and copper oxalate; and / or The aluminum source is selected from one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum acetate, and aluminum oxalate; The zinc source is selected from one or more of zinc sulfate, zinc chloride, zinc nitrate, zinc acetate, and zinc oxalate; and / or The coprecipitant is selected from one or more of alkali metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates, preferably alkali metal carbonates, and more preferably sodium carbonate.

9. The application of the composite catalyst according to any one of claims 1-8 in the one-step preparation of dimethyl ether from syngas.

10. A method for one-step synthesis of dimethyl ether from syngas, characterized in that, The method includes: Synthetic gas is catalytically converted into dimethyl ether in the presence of the composite catalyst described in any one of claims 1-8; Preferably, the conditions for catalytic conversion include: Synthesis gas contains CO, CO2, and H2; and / or The reaction temperature is 240-280℃; and / or The reaction pressure is 3-6 MPa; and / or In a slurry bed reactor; and / or The process is carried out in the presence of a liquid solvent; preferably, the liquid solvent is liquid paraffin.

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